Method of making mineral fibers of high corrosion resistance and fibers produced

ABSTRACT

Mineral fibers of high corrosion resistance are made by employing a base material or composition containing a plurality of oxides of metals from at least one of the groups II, III, IV and VIII of the Periodic Table; adjusting the base raw material or composition so as to furthermore include TiO2 in an amount of at least 1.5 percent by weight of the total composition and at least one oxide of a metal from the group II or IVa in an amount of at least 2.5 percent by weight of the total composition; melting the said raw material or composition; spinning the molten mass into fibers and then coating the thus-formed fibers with a polysiloxane resin. The fibers are particularly suited for incorporation in a cement medium where they may totally or partially replace asbestos fibers previously used for this purpose.

1136-85. At: 116 EX United States Patent [1 1 [1 11 3,854,986 Chvalovskyet al. 1 1 Dec. 17, 1974 METHOD OF MAKING MINERAL FIBERS 3,523,8038/1970 Haslay et al. 106/50 O HIGH CORROSION RESISTANCE AND 2,970,1221/1961 McLoughlin 117/126 X FIBERS PRODUCED [75] Inventors: VaclavChvalovsky, Praha; Lumir primary Examiner Roben L Lindsay 1 Mach; HelenaMac both of Attorney, Agent, or Firm-Michael S. Striker Ostrava, all ofCzechoslovakia [73] Assignee: Ceskoslovenska Akademie Ved,

Praha, Czechoslovakia [57] ABSTRACT [22] Filed: Sept. 26, 1969 [2]]App], NO; 861,471 of high corrosion resistance are made b'y'e'm' loyinga base material or composition contain- Related Apphcal'on Data ing aglurality of oxides of metals from at least one of 1 Continuation-impartf Sen o- 7 2.61 p the groups 11, 111, IV and Vlll of the Periodic Table;1968 abandonedadjusting the base raw material or composition so as tofurthermore include TiO, in an amount of at least 1 1 ForeignAppllcallon Priority Data 1.5 percent by weight of the total compositionand at Sept. 26, I967 Czechoslovakia 6819-67 least one oxide of a metalfrom the group 11 or Na in an amount of at least 2.5 percent by weightof the [52] U.S. Cl 117/126 GS, /3, 106/50, total composition; meltingthe'said raw material or 106/85, 106/99 composition; spinning the moltenmass into fibers and [51] Int. Cl. C03c 25/02 then coating thethus-formed fibers with a polysilox- [58] Field of Search 65/3; 106/50,99, ane resin. The fibers are particularly suited for incor- 162/154,156; 117/126 GS poration in a cement medium where they may totally orpartially replace asbestos fibers previously used for [56] ReferencesCited this purpose.

UNITED STATES PATENTS 3.095.311 6/1963 Von Wranau et a1. 106/50 12Claims, N0 Drawings CROSS-REFERENCES TO RELATED APPLICATIONS Thisapplication is a continuation-in-part of application Ser. No. 762,615filed by the same inventors on Sept. 25, 1968 now abandoned and assignedto the same assignee and relating to Method of Manufacturing andTreating Mineral Fibers Resistant in Cement Medium.

BACKGROUND OF THE INVENTION The present invention relates to amethod ofmanufacturing mineral fibers of high corrosion resistance.

This type of fibers is necessary for incorporation in a cement medium.The usual fiber type incorporated in cement is asbestos fibers. For manyyears efforts have been made to at least partially replace the asbestosfibers by cheaper man-made fibers. So far these efforts have not beensuccessful.

The essential point in this connection is the necessity to have a fiberwhich resists corrosion occurring in the hydrating cementous medium.This is a serious problem since, even with properly aged concrete types,a pH value is often reached amounting to about 12. In a medium of thiskind, conventional glass or mineral fibers are damaged to an extent suchthat the cement medium reinforced with these materials gradually losesmechanical strength. With certain types of fibers such as ordinary glassfibers and certain mineral fibers a complete degradation of the fibermay occur. Even basalt fibers which otherwise are highly resistantcannot resist the action of the hydrating cementous medium for anylength of time.

It has thus been impossible to obtain a good substitute for an asbestoscement or to obtain a less expensive form of asbestos cement or otherfiber-reinforced cementous media by means of mineral fibers or glassfibers in spite of the fact that these fibers have a relatively lowprice and rather high-grade parameters in connection with their use forstructural materials.

It has also been proposed to improve mineral fibers by including acertain amount of titanium in the fiber. This is supposed to improvetheir alkaline corrosion properties, but in order to really make thesefibers resistant to alkaline corrosion, the titanium content had to beincreased to or more percent constituted by titanium dioxide.

It has also been proposed to improve the resistance to alkalinecorrosion of glass fibers by coating the latter type of fibers withsilicone oil films. This process, however, has not been applied tobasalt fibers or fibers obtained from iron slags or similar rawmaterials. Besides, in order to provide for the necessary protection ofthe fiber. the coating had been necessarily quite thick resulting in areduction of the adhesion of the hydrated cement to the fiber and thusresulting in poor mechanical properties of the final product. This hasin particular prevented the use of mineral fibers for this purpose.

It is therefore an object of the present invention to provide corrosionresistant coated fibers and a method of making them in order to furnisha fiber suited for incorporation in a cement medium and in particularfor partial or complete replacement of asbestos fibers in so-calledasbestos cements. By this term there are included the so-called asbestosboards and asbestos lumber types of material.

SUMMARY OF THE INVENTION This object is met by employing a base rawmaterial or composition for the mineral fibers containing a plurality ofoxides of metals from at least one of the groups II, III, IV and VI ofthe Periodic Table and adjusting the basic raw material or compositionso as to include TiO in an amount of at least l.5 percent and at leastone oxide of a metal from group II or Na in an amount of at least 2.5percent by weight of the total composition; then melting the rawmaterial or composition and spinning the molten mass into fibers andfinally coating the thus-formed fibers with a polysiloxane resin.

The invention also embraces a mineral fiber obtained by the process justdefined and an asbestos cement in which from 5 to 50 percent of thefibers are replaced by the described mineral fibers. The invention alsocovers a reinforced cement product wherein from 2 to 30 percent of themineral fibers are constituted by the de scribed fibers of theinvention.

DESCRIPTION OF THE PREFERRED, EMBODIMENTS The basic raw material in thepresent case may be a comparatively inexpensive material such as a'basalt, dolomite or a clay or shale such as the North Bohemian clays orshale types. It may also be a slag obtained in iron metallurgy, forinstance from a blast furnace operation. It may finally be a specialslag obtained in a process for making colored metals and their alloyssuch as are obtained in the production of zirconium-silicon alloys andiron-titanium alloys.

The basic raw material will already have an increased resistance tocorrosion by the action of calcium hydroxide. The original basicmaterial may for instance have the following composition: 35-47% SiO5-l8% M 0 2-l5% FeO Fe,0,,, 2-23% CaO and l-30% MgO, the total of CaOplus MgO being from l4 to 38 percent, all percentages being given byweight of the total composition.

It is however important and a feature of the invention that the basiccomposition must be adjusted to contain certain minimum amounts oftitanium oxides and of at least one oxide of a metal in group II or IVaof the Periodic Table and preferably at least one oxide selected fromthe group of zirconium oxide (ZrO and zinc oxide (ZnO). The minimumamount of titanium oxide (TiO should be 1.5 percent and the minimumamount of the other two oxides or, if only one of them is used, of oneof the other two oxides, which preferably are zirconium dioxide and zincoxide, should be 2.5 percent. The maximum amount of zinc oxidepreferably is 2.5 percent and the maximum amount of zirconium dioxide ispreferably 5 percent.

For instance, the total composition after adjustment may be as follows:(percentages by weight of total composition) SiO, 35-47% A1 0,, 5-1 8%FeO Fe,O 2-l 5% CaO 2-2370 MgO l-307c MnO 0-l0% Na O K 0 below 5%Continued T10, l.5l% ZrO, 0-57: ZnO O-% CaF, 02%

In this composition the sum of CaO and MgO content should be between 14and 38 percent, while the sum of CaO, M g0, A1 0, and SiO, contentshould not be in excess of 90 percent of the total composition.

lt will be understood that some of the special oxides used to adjust thecomposition, such as TiO Zr0 and ZnO, may already be present in theoriginal raw material. The point is that, to the extent that they arenot present, additional amounts or additional oxides have to be added inorder to bring the amount of special components up to the desired value.Secondly, it is not possible to employ a basic material that has thenecessary components of titanium dioxide and for instance of zirconiumdioxide and zinc oxide. The original base material must meet therequirements regarding melting properties and also fiber formation. Itis therefore necessary that the composition of the original or basematerial is adjusted to the extent necessary by adding additionalamounts of titanium dioxide or for instance zirconium dioxide and/orzinc oxide in order to comply with the minimum amounts as stated.

Frequently, the additions are made in technical grades of materialcontaining considerable impurities. For instance, the zinc oxide whichmay be added may contain iron (lll) oxide and other components. Thezirconium dioxide normally is in the form of a silicate, for instance asobtained in the form of a zirconium slag or a so-called zirconiumconcentrate which may include other materials but should have the amountoloxide to provide for the necessary pure oxide in the melt. The basematerial is then subjected to conventional fiber melt spinning process.The temperature range for this spinning process and melting operationwill depend on the kind of raw material. The melting temperature may forinstance be in the range between l,360 and l,460C. After forming thefibers in conventional manner by the melt spinning operation, the fibersare then coated with a polysiloxane resin. More specifically, the

. resin should be a methylsiloxane polymer of the following formulawherein the sum ofx and y is less than or equal to 2 and preferablyequal to l or y is 0 and x is or is close to 2. The number of units ofthe above formula n may for instance be 200.

It will thus be seen that the fibers made by spinning a melt of thebasic composition which is adjusted if not containing the necessarycomponents to include a minimum amount of titanium dioxide and a certainminimum amount of at least one oxide from group ll or IV and preferablyof at least one oxide from the group of ZrO, and ZnO, and that thefibers thus obtained are then coated with the polysiloxane resin.

It has been found that the fibers thus produced meet all requirements asto adhesion to the bonding material, that is to the cement medium, aswell as regarding their mechanical properties, particularly theirresistance to alkaline corrosion. This is the case even though thesiloxane polymer film may be of extreme thinness. For

instance, the fibers may have a thickness of 3 denier or 75 am.

The amount of siloxane polymer resin may be for instance between 1 and 5grams of polymer dry solid substance per kg of fiber material. Thespecific amount will depend on the specific resin type used. A finergrade fiber will require a larger portion of siloxane polymer than acoarser type fiber, since the amount of siloxane necessary will dependon the total surface area of fibrous material which must be coated.

Preferably, the siloxane resin is a methyl polysiloxane resin such as adimethyl siloxane resin.

The methyl siloxane polymer reduces the corroding action of ions uponthe fiber mass. It may even prevent contact between the fiber and theions entirely. This notwithstanding, it does not appear to reduce theadhesion of the fiber to the cement bonding medium.

The methylsiloxane coating is applied to the fiber either in the form ofan emulsion or in the form of a spray mist containing the activesubstance. In both cases the film has to be heat-hardened before thefiber can be used.

It thus appears that as the result of the invention fibers made by thedescribed process have a sufficient resistance to the hydrating cementmedium and simultaneously also a good adhesion to the cement medium. Thecombination of these two properties could not be obtained withpreviously used glass or mineral fibers.

The following two examples will further illustrate the invention; allpercentages are by weight of the total composition.

EXAMPLE I A charge comprising percent olbasalt and 25 percent ofa blastfurnace slag was employed in this example. To this charge there wasadded. prior to melting, an amount of 5 percent of an impure zirconiumconcentrate containing zirconium oxide together with various otheringredients. After this adjustment, the charge was then subjected tomelting at a temperature of l,390C. The total composition of the meltafter adjustment was as follows:

SK); 39.5 by weight Al,O 10.1 Z: by weight CaO 2L5 Zn by weight MgO l5.8by weight Fe Q, 4.8 by weight Ti l.6 by weight 0.6 by weight N O+K,O3.1%byweight Z2), 3.0 k by weight The molten mass was then subjected tospinning by means of a stream of superheated steam in a conventionalmelt spinning operation. There were thus obtained fibers of a thicknessof 5 am.

The fibers were then coated by an emulsion containing 3 g methylsiloxaneresin of the formula CH SiO per kg of fiber material. The zirconiumconcentrate was an Australian concentrate" in which the zirconiumdioxide was present in about 60 percent by weight. It was thereforenecessary to add about 5 percent of this composition to arrive at anamount of 3 percent zirconium dioxide in the melt. The emulsion was thensubjected to heat-hardening by a thermal treatment. There was thusprovided a protective methyl siloxane resin film on the individualfibers. The thusmade fibers had a sufiicient amount of corrosionresistance to be used in a hydraulic cement and possessed good adhesionto the cement medium.

EXAMPLE 2 forcements in these elements may comprise between 2 and 30percent of the total mass of the concrete.

As for the type of cement to be used, this is of a conventional type.For instance, it may be Portland ce- The basic charge in this caseconsisted of a basalt 5 ment, slag-Portland cement, trass cement, or aspeidentified by its place of origin in Czechoslovakia as ZlAR NADl-lRONOM.

The corrosion resistance of this basic composition was increased byadding an amount of 5 percent of the total composition of rutile (TiOThe total charge then had the following composition:

% by weight l 4 2 KO .0 .0

per kg of fiber material. n in this formula having a value of about 200.

The further treatment, in particular the heathardening, followed Example1.

The fibers made by the processes described in above Examples 1 and 2were then tested and compared with I control fibers. The fiber controlfibers had been made two batches of similar basic compositions as usedin Examples 1 and 2 but without any additional adjustment of the charge.In particular, no titanium dioxide or rutile or any of the other specialoxides such as zirconium dioxide or zinc oxide had been added. Upon amicroscopic examination of the fibers after 30 days immersion in aCa(Ol-l solution, it was found that the fibers had distinct marks ofcorrosion. It will be noted that this is a comparatively short time ofexposure since the fibers are intended to be included in the cement forindefinite times.

The fibers may cause with the above two examples when subjected to thesame test showed no corrosion marks at all.

The fibers of the invention are useful in the first place forsubstitution of part or a larger part of the asbestos in asbestoscement. For instance, from 5 to 50 percent of the asbestos fibers maypreferably be replaced by the fibers of the present invention. Thefibers can furthermore be used as reinforcement for extremely thinconstruction elements, that is in so-called fiber-reinforced cementtypes. In this type of material the reinforcing element is constitutedby fibers uniformly distributed throughout the mass of the cement. Manydifferent products may be made from these types of cements, such asasbestos boards and asbestos lumber, the referred-to thin structuralelements may be used for making strands, nettings and similar products.The rein- 0 includes zirconium.

We claim:

1. Glass fibers coated with a polysiloxane resin wherein said glassfibers are formed of a glass having the following composition:

SiO; 3547% A1 0; 5-1 8% FeO FqO; 2-1 5% C210 2-23% MgO 130% MnO 0-l0%Na,O K,O below 5% T10, 15-10% 2:0 0-5% ZnO 0-5% CaF, 0-2% the sum of CaOand MgO being between 14 and 38 per cent and the sum of CaO, MgO, A1 0,,and SiO being 1 up to percent of the total composition.

2. Coated glass fibers according to claim 1 wherein said resin is amethylsiloxane polymer.

3. Coated glass fibers according to claim 2 wherein said methylsiloxanepolymer resin has the unit formula the sum ofx and y being less than orequal to 2.

4. Coated glass fibers according to claim 1 wherein said glass fibersare formed of a glass having the following composition SiO, 39.2% byweight A1 0, 10.1% by weight CaO 21.0% by weight MgO 15.8% by weightFe,O, 4.8% by weight T10, 1.6% by weight MnO 0.6% by weight Na O K 03.1% by weight 210, 3.0% by weight and said resin is a methylsiloxanepolymer.

5. Coated glass fibers according to claim 1 wherein said glass fibersare formed of a glass having the follow ing composition:

SiO, 45.6 by weight A1 0, 1 L0 $210 16.0 10.1 R58, 4.1 T10, 5.4 MnO 0.2Na O K,O 4.0 ZnO 3.0

and said resin is a methylsiloxane having the average formula wherein nis equal to about 200.

6. Process of making glass fibers coated with a polysiloxane resincomprising melting a glass having the following composition:

SiOba 354770 A] 5-1 8% FeO FqO, 245% CaO 243% MgO 140% MnO 040% N nobelow "n3, 1 540% no, o-5% ZnO 0-s% CaF, 0-2% the sum of CaO and MgObeing between 14 and 38 percent and the sum of CaO, MgO, M 0 being up to90 percent of the total composition, spinning the melt into fibers andcoating the thusly formed fibers with a polysiloxane resin.

7. The process of claim 6, wherein the polysiloxane resin is amethylsiloxane polymer.

8. The process of claim 7, wherein the siloxane resin has the unitformula a operation.

1. GLASS FIBERS COATED WITH A POLYSILOXANE RESIN WHEREIN SAID GLASSFIBERS ARE FORMED OF A GLASS HAVING THE FOLLOWING COMPOSITION;
 2. Coatedglass fibers according to claim 1 wherein said resin is a methylsiloxanepolymer.
 3. Coated glass fibers according to claim 2 wherein saidmethylsiloxane polymer resin has the unit formula
 4. Coated glass fibersaccording to claim 1 wherein said glass fibers are formed of a glasshaving the following composition
 5. Coated glass fibers according toclaim 1 wherein said glass fibers are formed of a glass having thefollowing composition:
 6. Process of making glass fibers coated with apolysiloxane resin comprising melting a glass having the followingcomposition:
 7. The process of claim 6, wherein the polysiloxane resinis a methylsiloxane polymer.
 8. The process of claim 7, wherein thesiloxane resin has the unit formula
 9. The process of claim 8, whereinthe sum of x and y equals
 1. 10. The process of claim 6, wherein thebase composition consists of basalt or dolomite.
 11. The process ofclaim 6, wherein the basic composition consists of a clay or shalematerial.
 12. The process of claim 6, wherein the base material consistsof an iron slag resulting from a blast furnace operation.